Technical Field
The present invention relates to a metal pillar, especially relates to a metal pillar with a cushioned tip which absorbs height differences among metal pillars.
Description of Related Art
FIGS. 1A˜1B Show a Prior Art.
FIG. 1A shows that a plurality of metal pillars 11A, 11B configured on a bottom side of a first device 11 and a plurality of metal pads 121 configured on a top side of a second electronic device 12. Each of the metal pillars 11A, 11B is configured to electrically couple to a corresponding one metal pad 121. However, height differences among metal pillars exist due to intrinsic process variation. For example, a height difference d1 occurs between metal pillar 11A and metal pillar 11B. The problem for the prior art is that the height differences d1 cause electrical connection problem. The shorter one metal pillar 11A may not contact the metal pad 121.
FIG. 1B shows similar problem occurs in metal pillars coupled to metal pillars. FIG. 1B shows that a plurality of first metal pillars 13A, 13B configured on a bottom surface of a third device 13 and a plurality of second metal pillars 142 configured on a top surface of a fourth device 14. Each of the third metal pillars 13A, 13B is electrically coupled to a corresponding one of the second metal pillars 142. However, height differences among metal pillars exist due to intrinsic process variation. For example, a height difference d2 occurs between metal pillar 13A and metal pillar 13B. The problem for the prior art is that the height differences d2 cause electrical connection problem. The shorter one metal pillar 13A may not contact the corresponding metal pillar 142.
A solution needs to be conceived to solve this problem, especially when the requirement for package technology is higher and higher for the swiftly developed semiconductor industry.